Packed red blood cell units destined for transfusion can be stored for up to 42 days prior to transfusion based on Food and Drug Administration (FDA) guidelines. Recent studies suggest that certain patients transfused with blood stored for longer duration have poorer outcomes than patients transfused fresher blood. The investigators' hypothesis is that the delivery of an immediate and substantial load of hemoglobin-associated iron from a stored unit of blood leads to changes that explain the differences in outcome between patients transfused old versus fresh blood. The investigators propose to test this hypothesis in humans by transfusing an individual's own blood, both fresh and after storage, and comparing levels of various outcome measures.